Microstructure and flux flow processes in superconducting MgB2 films
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StatusThe thesis was presented on the 1 March, 2006Approved by NCAA on the 27 April, 2006 Abstract – 0.44 Mb / in romanian – 0.39 Mb / in englishThesisCZU 537.312.62
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Keywords
superconductor MgB2, thin films, critical curent, critical field, activation energy, pininning forceSummary
The advanced method of high quality MgB2 film production of the first multi-band superconductor is proposed. The method includes DC Magnetron Sputtering of Bprecursor films and annealing of the precursors in a special designed self-sealing Nb container at defined temperature and pressure of Mg vapor. The invented process is confirmed by two patents.
For the first time the detailed investigation of the dependence of the superconducting properties on the structure and morphology of MgB2 films was performed.
The origin of the superconducting transititions broadening for MgB2 samples under high magnetic fields was clarified. Thermally activated flux flow (TAFF) in the MgB2 films under high magnetic field was monitored for the first time, a very strong field dependence of the activation energy of TAFF was found.
The outcome of the work enables to fabricate reliable high quality MgB2 layers for technical application, with a thickness of the films from 50 nm up to 5000 nm and the highest critical temperature of Tc= 39.4 K as well as a small width of the resistance transition ΔTc=0.3 K.
Acknowledgement:
This work has been done using „Coolpower-4,2GM“ closed-cycle He-liquifier and Nliquifier “PLN-106”, both donated by Alexander von Humboldt Foundation to the
Laboratiory of Superconductivity of Professor A.S. Sidorenko. For the possibility to do
research with this equipment the author is thankful to A.v.H.-Foundation.
Oficial Reviewers
- Teodor Şişianu
doctor habilitat, professor - Maria Palistrant
doctor habilitat, professor, Institute of Applied Physics of the
Theses
